Marijuana advocates were overjoyed this week when Illinois Gov. Bruce Rauner legalized medical cannabis as a substitute for prescription painkillers. The Marijuana Policy Project called it a “big win” for patients, and officials say it will greatly expand the number of patients, possibly saving lives.

But the new state law raises the question: How effective is cannabis for treating pain? And how well does it work to reduce opioid use and overdose deaths?

The answers, of course, depend on whom you ask, be it doctors, researchers or patients. Some pain physicians love it. Many addiction specialists, not so much. The National Institute on Drug Abuse has decades of research on the negative effects of marijuana, while the Center for Medical Cannabis Research in San Diego has mostly positive reports. And patients have their own preferences.

Some patients said they’re grateful for an alternative to pain pills that some say make them groggy.

But Joe Ruzich, who has a nerve disease that left him sometimes screaming in pain, said he only survives thanks to an electric stimulator and an opioid pump. He worries that doctors are being pressured to cut off opioid medication.

“It helps people like me live a normal life,” said Ruzich, who previously wrote for the Tribune as a freelance reporter but had to stop because of his ailment. “I’m glad people have more choice, but to present it as an alternative to opioids doesn’t seem right to me.”

As with many aspects of marijuana, research has found mixed results. The short answer is, yes, marijuana can help relieve pain, but not for all patients with all conditions. Some states with medical cannabis have also reported reductions in narcotics prescriptions, abuse and overdose deaths — though those associations don’t prove marijuana caused those changes.

Doctors agree that more research is needed. But the evidence so far hasn’t stopped advocates on both sides from either praising cannabis as the cure for everything from cancer to gout, or condemning it as a scourge that can cause users to become psychotic.

With an election for governor coming in November, the topic has become a campaign issue, with Rauner opposing legalization for recreational use and Democratic opponent J.B. Pritzker supporting it. Activists and opponents alike have been lobbying to influence public opinion.

The day after the new medical cannabis law was approved, one Illinois producer, Cresco Labs, announced a related marketing campaign, including a vending machine installed at the state of Illinois’ Thompson Center in Chicago that looked like it dispensed narcotic pills, but instead put out information promoting medical cannabis.

Jose M. Osorio/Chicago Tribune

Dannielle Mares stops to look at vending machines filled with narcotics bottles at the Thompson Center in Chicago on Aug. 29, 2018. The vending machines are used by Cresco Labs to promote medical cannabis as an alternative to opioids.

Dannielle Mares stops to look at vending machines filled with narcotics bottles at the Thompson Center in Chicago on Aug. 29, 2018. The vending machines are used by Cresco Labs to promote medical cannabis as an alternative to opioids. (Jose M. Osorio/Chicago Tribune)

As Dr. Ajay Wasan explained in his recent MedPage Today article, “I Didn’t Study Medicine to Prescribe Weed,” many doctors remain reluctant to authorize medical marijuana use. But he welcomes the opportunity to try a promising new treatment with caution.

Wasan is an anesthesiologist and a professor at the University of Pittsburgh, and is on the board of directors of the American Academy of Pain Medicine in Chicago. Pennsylvania has a new law similar to that in Illinois, allowing the use of marijuana to try to wean patients off opioids.

Most people who legally use prescription pain pills don’t abuse their medicine, he said. About 30 percent of his patients have been successful at reducing or eliminating opioid use with the help of cannabis under a doctor’s care. Some, he said, don’t like marijuana at all and prefer not to use it.

“It’s not a home run, but the balance tilts toward the positive,” Wasan said. Certain types of pain, such as pain related to nerve damage, have a much greater likelihood of responding than others, such as fibromyalgia.

And for those who use illegal opioids, there is not sufficient data showing that marijuana helps them stay clean.

Research so far has generally backed up claims for some types of pain relief. In the most recent comprehensive review of marijuana’s effects, the National Academies of Sciences, Engineering and Medicine last year found evidence that patients using cannabis were more likely to experience a “significant” reduction in pain.

Marijuana also decreased muscle spasms in some people with multiple sclerosis and reduced nausea and vomiting in some cancer patients on chemotherapy. But the review also found evidence that the drug is likely to increase the risk of schizophrenia, other psychoses and social anxiety disorders — and there was moderate evidence linking marijuana to abuse of other substances.

Major medical groups like the American Medical Association and the American Academy of Family Physicians oppose state medical marijuana laws. The American Society of Addiction Medicine says all cannabis products should be subjected to the same standards and federal approvals of prescription medications, and that smoking it as a delivery method should be rejected because of its health hazards.

Dr. Norm Wetterau, president of the New York Society of Addiction Medicine, said cannabis “does help for terminal cancer pain” but that advocates “say it’s good for everything that ails you. There’s no evidence for that.”

The FDA has approved two synthetic versions of THC, the primary psychoactive component of marijuana, and this year for the first time approved an oil containing the nonpsychoactive component cannabidiol, or CBD, for treatment of rare forms of epilepsy.

But federal law still classifies the marijuana plant as a highly addictive schedule I substance with no accepted medical value, the same category as heroin and LSD. Meanwhile, opioids killed an estimated 70,000 people last year in the United States — about 40 percent of them from legal prescription drugs like hydrocodone, oxycodone, codeine and morphine.

There is a lack of controlled studies on using cannabis to get off narcotics. But one survey of almost 500 patients using marijuana for medical purposes in Canada found that 80 percent reported substituting it for prescription drugs. Skeptics point to a recent Australian study in The Lancet journal that showed people who used marijuana for chronic pain over several years actually reported more pain than those who didn’t.

That result is one that Dr. Mark Wallace runs into commonly at his pain clinic: patients who try to self-medicate with marijuana but use too much, and their pain increases.

Wallace is an anesthesiologist who conducts cannabis research at the University of California at San Diego and he’s on the board of the American Pain Society in Chicago.

“I see patients every week wanting off opioids,” he said. “It’s a drug that will grab hold of a patient and will not want to let them go. Their life revolves around their next dose. That behavior changes when I put them on cannabis.”

He cites research and his own patients’ experience showing there is a therapeutic window for cannabis — where high CBD and low amounts of THC, around 4 percent — can reduce pain, but high amounts make it hurt more. For some patients, marijuana takes the edge off withdrawal symptoms and helps them sleep, which is a big benefit.

“After years of (prescribing) both, I believe we should use cannabis before an opioid,” Wallace said.

Doctors need training on dosing before they will feel comfortable certifying patients to use cannabis, he said.

“If you don’t do controlled dosing,” he said, “patients will get worse.”

As for what the manufacturers of opioid-based prescription painkillers think of marijuana as a substitute, and of Illinois’ new law, the industry has been tightlipped. More than a half dozen companies or industry groups contacted by the Tribune provided no response.

A spokesman for the one company that did, Purdue Pharma, which makes OxyContin, said only that it supports patient access to FDA-approved medications.